Instead of lecturing users by sudo's default lecture message:

We trust you have received the usual lecture from the local System
Administrator. It usually boils down to these three things:

    #1) Respect the privacy of others.
    #2) Think before you type.
    #3) With great power comes great responsibility.

and threating them after they have futilely typed their password:

[username] is not in the sudoers file. This incident will be reported.

It is better to prevent the users from even trying and show them a friendly warning for education purpose, by setting the following in /etc/sudoers:

Defaults lecture = always
Defaults lecture_file = /etc/sudo-lectures.txt
Defaults passwd_tries = 0

Such approach can be extended further to display different messages each time a sudo attempt is performed. Our Python script uses inotify to monitor lecture_file and alter its content whenever it is opened and displayed to some users.

The script sudo-daemon will read the filepath of lecture_file via an environment variable: SUDO_LECTURE_FILE.

python setup.py install
export SUDO_LECTURE_FILE=/etc/sudo-lectures.txt
sudo-daemon